Thread rolling device



March 1955 E. T. scoTT THREAD ROLLING DEVICE 2 Sheets-Sheet 1 Filed June 14. 1951 5 1m er T; Sc 0 (Ittormg March 1955 E. T. SCOTT THREAD ROLLING DEVICE 2 Sheets-Sheet 2 Filed June 14, 1951 3nvcntor Elmer sco d:

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Grim-neg United States Patent THREAD ROLLING DEVICE Elmer T. Scott, Worcester, Mass., assignor to Reed Rolled Thread Die C0., Holden, Mass., a corporation of Massachusetts Application June 14, 1951, Serial No. 231,560

3 Claims. c1. 80-6) This invention relates to a thread rolling device, and more particularly to that type which has freely rotatable rolls engaging a positively driven work piece.

device of the type herein described is primarily adapted for mounting on a turret lathe or other suitable machine and is arranged to roll a thread in a cylindrical work piece that is positively rotated by the machine tool headstock while the dies are forced directly into the wor The primary object of this invention is to provide a device which will roll a thread accurately and etficiently, and wherein the rolls are balanced in their action and apply the same pressure on the work as they are moved progressively through equal distances toward the work axis during the rolling operation.

A further object is to provide a device of this type having two rolls which are pivotally mounted to be swung through arcs during the feeding operation and will retain contact with the work on a diameter thereof.

Another object is to provide a device in which both ends of the roll axle are so mounted on swinging supports that the rolls may be readily replaced by others of different diameters or widths.

Another object is to provide a thread rolling device of this type in which the rolls may be prelocated relative to the work so as to minimize the required arcuate travel of the roll for starting the thread rolling operation.

Another object is to provide for adjusting the position of one roll relative to the work center so that each roll engages the work at the same time and they roll the thread simultaneously to the same depth.

A still further object is to provide a device of this type in which the rolls are returned automatically after a rolling operation to a Work receiving position. Other objects will be apparent in the following disclosure.

Referring to the drawings:

Fig. l is an isometric view of the device with the rolls in an open position ready to receive a work piece;

Fig. 2 is a similar view with the roll supports tilted and the dies in rolling engagement with the work;

Fig. 3 is an isometric exploded view of the stationary core, a rockable die support and a locking device to hold the die on the core;

Fig. 4 is an isometric view of the housing which serves to rock the die carriers for the rolling operation;

Fig. 5 is an end view of the same type of device which is modified to provide for die roll adjustments;

Fig. 6 is a side view of the same showing the core in a split housing but with one die roll removed; and

Fig. 7 is a side view, looking in the direction of the line 77 in Fig. 6.

This thread rolling device comprises two relatively rotatable members, one of which rockingly supports the die rolls and the other serves to apply pressure for rocking the dies towards the work axis. In the preferred construction, the die roll supporting member is held stationary on the machine tool and the die rolls are supported thereon for an eccentric rocking movement relative to the work, and the pressure member is rotated by the cross slide or other mechanism about the work axis and arranged to rock the eccentric die roll carriers. The construction illustrated has a stationary core 10 carried by a shank 11 adapted to be fixedly mounted on the turret or other part of a suitable machine and with the shank and associated parts axially aligned with the work piece to be threaded. A set of spaced dies 12, and preferably 2 dies, are mounted radially of the work for free rotation 2,704,950 Patented Mar. 29, 1955 on spindles 13 removably held in a yoke-shaped rocking carrier 14. The dies 12 are provided with threads in accordance with standard construction which are arranged to roll a thread in a work piece W (Fig. 2) as the dies are pressed progressively into the positively rotated work surface therebetween.

Each yoke or die roll carrier 14 has a pivot shank or pin 15 projecting from the rear side of one yoke arm which pivotally fits within a cylindrical bearing hole 16 in the core 10, the axis of the shank being parallel with but eccentric to the axis of the work. As illustrated, the core 10 has a cylindrical disc shaped body arranged at right angles to the axis of the shank 11, and it is further provided with a set of lugs 17 which have convex partial cylindrical surfaces forming a continuation of the cylindrical periphery 21 of the disc. Each lug 17 has a concave partial cylindrical surface 18 that is concentric with the hole 16 but is spaced a short distance therefrom, as shown particularly in Fig. 3. Each yoke shaped die roll carrier 14 is provided with a partial cylindrical convex surface 20 (Fig. 3) which rockingly fits against the concave surface 18 on the core 10. lhe surfaces 18 and 20, therefore, supplement the pivot shank 15 and its hearing 16 in rotatably supporting the yoke carrier and its die. The exploded view of Fig. 3 shows how the surface 20 may be moved axially into contact with the surface 18 and the pivot shank 15 thrust into the bearing opening 16. Each lug 17 has a threaded hole 22 therein (Fig. 3) adapted to receive a cap screw 23 which serves to secure a locking member 24 in place to hold the rocking die carrier or yoke 14 in position. That locking member 24 has a partial cylindrical concave surface 25 adapted to fit against a partial cylindrical convex surface 26 of the yoke carrier 14, which is concentric with the outer or higher surface 20 at its side, and so aids in supporting the outer yoke arm of the die carrier. This locking member also has a rib 27 projecting outwardly therefrom which serves to hold the die carrier against endwise movement, as will be described. This rib 27 is concentric with but raised above the convex partial cylindrical surface 28 which is concentric with the work axis and is in alignment with the outer periphery 21 of the core 10.

Each thread rolling die 12 is eccentrically mounted relative to the axis of the pivot shank 15 and the supporting are 18 on the core, so that any rotation of the yoke support 14 will serve to move the die through an are relative to the center of the work, the latter being arranged to pass concentrically into the central space within the disc 10 and its shank 11. The two dies 12 and their axles 13 are so located that the dies will always contact with the outer work periphery on a diameter of the work, since the two bearing openings 16 in the core 10 are located on a diameter of the work and the die mounts are symmetrical but oppositely arranged for equal movement.

The simultaneous rocking motion of the dies is effected by means of the pressure member or housing 30 (Fig. 4) which is hollowed out and provided with an internal partial cylindrical face 31 concentric with the work axis and shaped to rotatably fit on the cylindrical face 21 of the disc of the core 10 and the cylindrical surface extensions provided by the lugs 17 and locking member 24. The housing is provided with a slot 33 adapted to interfit with the projecting rib 27 of each locking member 24 when the housing and core have been assembled axially.

This rib 27, therefore, serves as a key to hold the housing in a definite position relative to the core but permits rotation of the housing about the stationary cylindrical surface 21, as is required for forcing the die rollers 12 into the work piece. The key member 24 also presses against the side of the rib 20 of the die roll carrier 14 and so holds it against endwise movement.

The housing or pressure member 30 is preferably provided with an adjustment screw 35 suitably located for engagement by a pusher on the cross slide of the lathe or other machine tool on which the device is mounted. By adjustment of the screw 35, the relative positions of the lathe cross slide and the housing may be varied as needed, so that the travel of the cross slide will give the required movement of the die rolls 12 into the work.

The housing 30 has two narrow projecting lugs prov1ding surfaces 36 parallel with the work was WhlCh are so arranged that each pushes against the flat surface 37 of the adjacent roll supporting yoke 14. The d1e carr1er 14 is substantially a slotted parallelopipedon hav ng the curved surfaces 20 and 26 projecting from one side adjacent to the flat face 37 of the carrier. The yoke support 14 moves about the center 38 of the surfaces 20 and 26 and the axle 15, so that the rotation of the housing 30 clockwise in Figs. 1 and 2 will push each yoke 14 in the general direction of the arrow and cause the die roll 12 supported thereby to be moved in that same arcuate direction. Since the pusher member 30 is an integral body, it serves as a yoke connecting the pusher surfaces 36, and the various parts are reversely symmetrical in shape and arrangement, so that the die roll carriers 14 will be moved simultaneously and to the same extent by rotation of the housing relative to the core 10.

When the pressure of the cross slide is released, the die rolls should be likewise released from the work. This is effected by means of a pair of springs 40 mounted in arcuate slots 41 formed in the inner vertical face 42 of that annular portion of the housing 30 which surrounds the cylindrical surface 32 of the core 10. The face 42 is perpendicular to the work axis and the spring slots 41 are concentric with that axis. The internal cylindrical surface 43 (Fig. 4) at the rear of that face 42 is rotatably mounted on the cylindrical surface 44 of the shank 11 and concentric with the shank axis. The surfaces 43 and 44 form the major rotational bearing support for the housing 30. The spring 40 in each slot engages two balls 45 at its opposite ends, one of which presses against the end of the arcuate slot 41 and the other presses against a pin 46. This pin 46 is fixed in the rear face of the core 10 in an extension of each screw hole 22 (Figs. 3 and 6) and projects from the rear of the disc-shaped core 10 and into that slot 41 of the housing. Since the pin 46 is stationary while the housing 30 is rotatable relative to the core, the rotation of the housing clockwise (Fig. 4) serves to compress the spring against the pin 46 and thus to store a force capable of returning the housing to its initial position when pressure is released from the adjustable pusher screw 35.

In order to return the yoke support 14 and its die 12 to an initial opening position relative to the work axis, a cam follower pin 48 (see Figs. to 7) is fitted tightly into the rear of the back arm of the carrier yoke 14 and arranged to travel in a cam slot 49 in the front face 50 of the housing (Figs. 2 and 4). The slot extends in such a direction and the pin fits loosely enough in it so that the pin may ride downwardlv in the slot to its lowermost position when each die roll has been swung to a fully closed or final position against the work. As the swinging arm of the yoke 14 moves in an are about the center 38 in a work rolling direction, the pin 48 moves down to the lowermost position in the slot 49, and the slot is so shaped as to permit this movement. When, however, the pusher housing 30 is thrust back by the spring 40 to its initial position, the cam slot 49 thrusts against the pin 48 and causes it to move upwardly to remove the dies from the work and leave them in the open position.

Another feature of the construction (omitted in Figs. 1 to 4) comprises means for prelocating the rolls and adjusting them relative to one another, so that they may have a simultaneous contact with the work and press into the work to equal depths. To this end, the housing 30 is made in two pieces, such as would be formed by cutting the housing along the dotted lines 52 in Fig. 4. This provides an adjustment piece 53 (Figs. 5 to 7) which is secured to the main portion of the housing 30 by means of two cap screws 54 threaded into holes in the piece 53 and having their enlarged heads riding in an elongated arcuate slot 56 in the main body piece 30. The slot provides clamping shoulders 57 against which the under sides of the heads 55 may be set to hold the block 53 in an adjusted position. A push screw 58 is threaded into the main portion of the housing 30 and engages an inner face 59 of the piece 53 which is normally spaced by a sufficient distance from the adjacent inner face of the main part of the housing so as to provide for a rotative movement of this piece 53 relative to the housing 30. It will be seen by reference to Fig.

4 that the piece 53 is an L-shaped block carrying a portion of the part cylindrical surface 31 and the slot 33 which constitutes a bearing for the key 24 and the surface 21 of the core 10. The adjustment of the piece 53 is necessarily around the peripheral face 21 of the core. This separate piece 53 also carries one cam slot 49 and so controls the position of the pin 48 in the rear of the related rocking yoke support 14. Thus, manual adjustment of this piece 53 will serve to move the associated die roll 12 to a desired position relative to the other die roll and the work axis, and the piece 53 may then be clamped tightly in position by means of the cap screws 54. It is not necessary to adjust both die rolls, since the movement of one relative to the other serves to bring them into a proper relationship with the work. Hence, the housing 30 need have only one adjustment piece 53.

As shown in Figs. 5 to 7, a further adjustment involves rotating the housing relative to the core and thus swinging the two die rolls simultaneously toward or from the work axis. To this end, the core is provided with a notch 60 in its periphery, and the housing has a push screw 61 threaded therein and arranged to engage a face of that notch and to adjustably move the housing 30 peripherally around the core 10. This adjustment gives a simultaneous and equal movement of both die rolls relative to the work and adjusts the radial spacing between the die rolls and the work, and so adjusts the roll positions for different work sizes and minimizes the required arc of travel of the housing to bring the rolls into contact with the work.

The shank 11 may be made hollow and provided with an opening 64 into which the work piece may be thrust and there be suitably supported by a work carrier or a centering device located in that cylindrical hole. Various other details of construction may be incorporated in the device as required. It will also be appreciated that if a die roll of a narrow width is required, it may be provided with a hub to engage the inner sides of the yoke 14 and thus hold the roll against endwise movement, or a collar may be placed on the axle pin 13. However, a slight axial movement of the roll may be permitted to give the roll a chance to adjust itself into a proper tracking relationship. The pin 13 is readily removable, and a new roll may be quickly inserted in the carrier or swinging arm 14. It will also be appreciated that the constructions of Figs. 5 to 7 are the same as those of Figs. 1 to 4 except as to the described adustment details and that a simplified form of device may be used without such adjustments. It mav also be noted that the housing is cut away on the line 63 (Fig. 5) to provide clearance for the movement of each carrier 14.

The operation of the thread rolling device will be apparent in view of the above disclosure. The die rolls will ordinarily be held in an open position by the spring 40 and the cam 49, so that the work piece W may be inserted therein. One end of the work, as is Well understood, is suitably mounted on and for rotation with the positively rotated headstock of a lathe, for example, and if desired the other end may be mounted on a tailstock centering device inserted within the hole 64 (Figs. 3 and 6) of the core 10 and its shank. The dies 12 are alike in shape and size and they are provided with threads which match those to be impressed in the work. The operation is essentially that of a plunge type of movement, in which the dies are forced directly into the work and radially thereof and are caused to roll the work by displacement of its metal into the thread grooves of the dies. Each die is freely rotatable on its axle 13 and so adjusts its position automatically relative to the rolled thread. The surface 36 of the housing or pressure transmitting body 30 thrusts against the surface 37 of each die carrier 14 when the housing 30 is rotated clockwise on the stationary core 10 by a thrust member on the lathe, such as when a part on the lathe cross head contacts and pushes against the adjustment screw 35 at the lower side of the housing 30. The bearing sockets 16 for the axles 15 of the roll die supports 14 are held stationary and fixed diametrically of the work by means of the core 10 which is suitably clamped on the lathe. The die axles 13 are eccentric relative to the axles 15 or their center lines 38. Hence, when the die carrier 14 is thrust forward clockwise by movement of the housing 30, each die roll 12 must swing about the axis 38 in the general arcuate direction of the arrow in Fig. 2, and this swinging movement causes the dies to move gradually towards the work axis and at the same time to swing through a few degrees around the work. Since the centers of the roll dies 12 are positioned on a diametrical plane through the work at the start of the operation and the dies are moved equally and in opposite directions by the thrust imparted by the housing 30, then these die rolls 12 must remain in a diametrical arrangement relative to the work axis as the thread is rolled.

The various adjustments will take care of different conditions as to work size, machine construction and the rolling operation. The screw 35 will adjust for the relative positions of the cross slide of the lathe and the housing 30 of this device, so as to avoid unnecessary motion of the cross slide. The formation of the housing body 30 in two parts, comprising the L-shaped block 53 of Figs. 5, 6 and 7, makes it possible to adjust the separate member 53 peripherally of the core 10 and to move one roll die independently of the other radially of the work so that the two dies may contact the work simultaneously and roll to equal depths. The pin 46 projecting rearwardly from the stationary core 10 engages the spring 40 in the main body of the housing 30 and serves to return the housing to an mittal position irrespective of any adjustment of the part 53. On the other hand, the cam slot 49 is located in the adjustable block 53. Hence, circular movement of that block 53 about the core 10 by means of the adjustment screw 58 affects the position of the pin 48 and so swings the upper die roll carrier 14 relative to the work. Only one of the die rolls needs to be thus adjusted.

The housing or pressure member 30 may be swung around the core 10 by adjusting the screw 61 which passes through the housing wall into contact with a notch in the core. Since this moves the entire housing 30, including the separately adjustable L-shaped block 53, the adjustment of the screw 61 moves both of the rolls towards or away from the work axis. This serves to set the die rolls in a desired starting position relative to work pieces of dilferent diameters, and so avoids unnecessary motion of the rolls in approaching the work. Thus this construction serves not only to roll a thread with the die rolls always engaging the work on a diameter, but it gives desirable adjustments so that the rolls may be accurately positioned relative to the work axis and adjusted to avoid waste of time and unnecessary movement of the rolls while in a non-rolling position relative to the work.

It will be appreciated that various modifications may be made within the scope of this invention, and that this description of preferred embodiments is to be interpreted as not imposing limitations on the appended claims.

I claim:

1. A thread rolling device comprising a central body having a shank adapted to be fixed on a work rotating machine tool, a housing concentrically mounted for free rotation through a small angle about said body, a pusher contact on the housing arranged for engagement by a movable member on the machine tool to rotate the housing, two thread rolling die rolls, yokes rockingly mounted on the body eccentric to the housing axis which pivotally support the die rolls in axial parallelism and for movement around and diametrically of a rotated work piece therebetween, said housing having relatively adjustable members separately engaging said yokes and arranged to rock the die rolls at the uniform rate of housing movement and progressively towards and into the work surface to roll the work thread by a direct mfeed of the rolls, and cooperating adjustment devices on said housing members for independently rocking one member and fixing it relative to the other and thereby adjusting the associated die roll relative to the other die roll and the work axis.

2. A thread rolling device comprising a central body having a cylindrical periphery and a shank adapted to be fixed on a work rotating machine tool which has a reciprocable member, a housing concentrically mounted on and freely rotatable through a small angle around said periphery during the rolling operation, a pusher contact on the housing arranged for engagement by the reciprocable member on the machine tool to rotate the housing, two freely rotatable thread rolling die rolls, yokes supporting the die rolls in axial parallelism, pivots carrying the yokes which are rockingly mounted on the body eccentric to the housing axis for moving the die rolls towards a rotated work piece therebetween, said rotatable housing having lugs directly engaging said yokes and arranged to rock the yokes at the uniform rate of housing movement during the entire operation and force the die rolls progressively towards and into the positively rotated work to roll a thread thereon, and a spring and associated members engaged by the spring located respectively on the housing and the yoke supporting body which reverse the housing movement when the machine tool pressure thereon is released and a cam and a follower respectively mounted on the housing and a yoke which cause the yoke to swing its die to an initial position when the housing movement is reversed.

3. A thread rolling device comprising a stationary central body having a cylindrical periphery, a shank on said body which is adapted to be fixed on a work rotating machine tool provided with a reciprocable part, a housing having an internal bearing surface riding on said periphery and freely rotatable through a small angle, a pusher contact on the housing engageable by the reciprocable part on the machine tool to rotate the housing in an operative work rolling direction, two freely rotatable thread rolling dies, yokes rotatably supporting said dies in axial parallelism relative to a work piece therebetween, said body having axially parallel bearing openings equidistant from and arranged diametrically of the axis of the periphery, each yoke having a supporting pivot pin axially parallel with and eccentric to the axis of said periphery which projects laterally into said bearing openings, said body and'yokes having concentric contacting bearing surfaces supplemental to the yoke pivot pins which aid in supporting the die rolls, lugs on the housing separately contacting the sides of the yokes for swinging them as the housing rotates and only at the rate of housing rotation, a spring and contact parts on the housing and body which reversely urge the housing towards an initial position, and a cam and a follower mounted respectively on the stationary body and each yoke which return each yoke to an initial position and maintain contact betwetn the lug and yoke when the housing is reversely rotate References Cited in the file of this patent UNITED STATES PATENTS 1,017,892 Landis Feb. 20, 1912 1,979,024 Bysshe Oct. 30, 1934 2,436,975 Ross Mar. 2, i948 FOREIGN PATENTS 122,997 Sweden Oct. 12, 1948 591,176 Great Britain Aug. 11, 1947 

